Carbon Monoxide: A Deadly Poison and Neurotransmitter
Carbon monoxide in the environment is a deadly poison that kills hundreds of people in North America every year. Unlike some poisonous gases, carbon monoxide is produced by devices that we have in our homes as well as by industrial processes. It's a colorless, odorless and tasteless gas and an insidious poison. We may not realize that we are being poisoned by carbon monoxide, since one of its effects is to make us confused and sleepy.
Strangely, this very toxic gas is a normal component of our bodies, where it's present in tiny quantities. It plays an important role in our nervous system and acts as a signaling molecule. Signaling molecules carry "messages" within or between cells or from one part of the body to another. A signaling molecule works by triggering a specific effect when it reaches its new location.
The chemical formula for carbon monoxide is CO. It's a simple molecule that is made of one carbon atom and one oxygen atom. This simple molecule has big effects, however, depending on its concentration. According to the CDC (Centers for Disease Control and Prevention), in the United States between 400 and 500 people die from CO poisoning every year. In addition, more than 20,000 people need to visit the emergency department of a hospital due to CO exposure and more than 4,000 people need to be hospitalized. On the other hand, endogenous carbon monoxide (CO made inside the body) seems to be vitally important in the normal functioning of our bodies.
Sources of Carbon Monoxide
Carbon monoxide is produced by the incomplete combustion of a fuel. Any device that burns gas, oil, kerosene, coal, charcoal or wood can produce carbon monoxide.
Devices that may release carbon monoxide in and around a home include furnaces, water heaters, gas stoves, propane space heaters, portable generators, charcoal grills, car engines and fireplaces. Gasoline-powered lawn mowers, leaf-blowers, weed trimmers, chain saws and snow blowers are also potential sources of CO.
Unfortunately, every year some people who have tried to keep warm in winter have died of carbon monoxide poisoning. Space heaters and stoves are frequently responsible for these deaths, which usually occur during power failures. Propane space heaters should never be used indoors and a gas stove should never be left on to warm a home.
It's a good idea to plan how to keep warm before a potential power failure occurs. If you have elderly acquaintances, you might want to help them prepare for a power failure, too. It would also be a good idea to visit them when there is no power to see how they're doing. Elderly people and babies are much more susceptible to health problems in cold temperatures than people of other ages.
Why is Inhaled Carbon Monoxide Dangerous?
Our red blood cells contain a protein called hemoglobin. Hemoglobin's function is to transport oxygen from the lungs to the body's cells, which use the oxygen to produce energy.
Carbon monoxide joins to hemoglobin, producing a substance known as carboxyhemoglobin. Carboxyhemoglobin can't carry as much oxygen as normal hemoglobin. The carbon monoxide also causes the hemoglobin to hold on to the oxygen molecules that have managed to join to it very tightly, preventing them from being released to the cells.
Researchers think that inhaled carbon monoxide hurts us in other ways besides blocking a cell's oxygen supply. It joins to myoglobin, a protein in muscle. This may cause muscle weakness. Carbon monoxide may also affect the functioning of the mitochondria, the structures in cells that produce the energy which we need.
An OSHA (Occupational Safety and Health Administration) Video about Carbon Monoxide
Symptoms of Carbon Monoxide Poisoning
The symptoms of carbon monoxide poisoning may at first mimic the effects of the flu or other disorders. If an affected person stays in the dangerous environment they may become confused and fatigued. At this stage it may be hard for someone to voluntarily evacuate from the dangerous area.
The most common symptoms of carbon monoxide poisoning are as follows:
- chest pain
- shortness of breath
A person who is suffering from carbon monoxide poisoning needs to be removed to an atmosphere with fresh air. They may need to receive supplemental oxygen as well. Even when the person has apparently recovered they should be taken to hospital.
Preventing CO Poisoning
A Carbon Monoxide Detector Poll
Do you have carbon monoxide detectors in your home?
Prevention of Carbon Monoxide Poisoning
Carbon monoxide poisoning may have devastating consequences, but it can be prevented. The most important precautionary steps are to use equipment in safe conditions and to have working carbon monoxide detectors in the home. Here are some safety tips.
- Place a carbon monoxide detector on every floor of your home, especially near sleeping areas.
- Make sure that detectors that are connected to an electrical outlet have a battery backup.
- Replace the batteries in carbon monoxide detectors regularly on easily remembered dates, such as family birthdays or the days when clock times change.
- Get equipment such as furnaces and water heaters serviced once a year.
- Make sure that devices such as stoves and fireplaces are vented.
- Get chimneys cleaned regularly.
- Don't leave a car running in a garage, even when the garage door is open.
- Don't turn on gas-powered equipment such as chain saws in enclosed spaces.
- Don't turn on generators in or near a home.
- Never use a propane or kerosene space heater or a charcoal grill indoors.
Carbon Monoxide as a Neurotransmitter
Carbon monoxide and two other dangerous environmental gases - nitric oxide and hydrogen sulfide - are present in our bodies in very small quantities. These gases appear to play a vital role in a wide range of body processes.
One process involving CO is the transfer of nerve impulses from one neuron, or nerve cell, to another. This transfer is called neurotransmission and is carried out by chemicals. The chemicals are known as neurotransmitters. Carbon monoxide, nitric oxide and hydrogen sulfide are all neurotransmitters. They behave a little differently from other neurotransmitters, however.
Most neurotransmitters are stored in sacs called vesicles at the end of a neuron. The vesicles release their neurotransmitter molecules when a nerve impulse arrives. The neurotransmitter molecules travel across the gap that is present between neurons and bind to receptors on the membrane of a second neuron. Once this union takes place, a new nerve impulse is generated in the second neuron. Some neurotransmitters have the opposite effect and stop a new nerve impulse from being generated.
Carbon monoxide and the other gaseous neurotransmitters aren't stored in vesicles but are rapidly made when they're needed. In addition, they don't bind to receptors on the second neuron but move into the neuron. Like other neurotransmitters they regulate the passage of the nerve impulse. They may actually act as neuromodulators instead of neurotransmitters, at least in some parts of the body. Neuromodulators influence the action of neurotransmitters instead of being neurotransmitters themselves.
Carbon monoxide, nitric oxide and hydrogen sulfide are sometimes called gasotransmitters instead of neurotransmitters. They seem to have similar functions in the body, but they sometimes work in different ways from each other.
Other Functions of CO
Researchers have discovered some specific functions of carbon monoxide in the body.
- It relaxes the muscles in the blood vessels, causing the vessels to widen and blood pressure to decrease.
- In rats, it protects against cardiac ischemia (a restriction in blood flow to the heart).
- It causes relaxation of the muscles responsible for gut contraction.
- In lab experiments with animals it reduces inflammation.
- In the brain, carbon monoxide modulates the release of other neurotransmitters.
Gasotransmitters in the Future
Scientists suspect that gasotransmitters could be used as medications if we understood their behavior better. In 2011 an organization called the European Network on Gasotransmitters, or ENOG, was created. The network holds regular conferences, meetings and workshops. Its aim is to discover the functions and methods of action of the different gasotransmitters and to develop their use as medications. The network also wants to discover the differences and similarities in the actions of the three gasotransmitters - carbon monoxide, nitric oxide and hydrogen sulfide.
It's interesting to realize that a potentially deadly gas such as carbon monoxide could have important health benefits. There is so much that we still need to learn about the human body. Understanding more about the action of carbon monoxide and the other gasotransmitters could lead to significant medical advances.
© 2013 Linda Crampton